Inductive proximity sensors are used as contactless switches in a harsh environment. An important quality feature in this respect is the maximum achievable switching distance.
An important quality feature of inductive sensors in addition to the amount of a nominal switching distance SN, that is defined for steel, is also the amount of the real switching distance that is achieved with other materials. These switching distances are determined by so-called reduction factors. The greater the switching distance or the reduction factor, the better. The sensor ideally has the same high switching distance for any desired metals. The reduction factors in this case have the maximum value 1 and are therefore called factor 1 sensors or F1 sensors.
Average inductive sensors typically only have a two-fold switching distance, no F1 property, and usually plastic housings having a plastic front face.